Introduction

The new experimental plugin is based on Gradle’s new component model mechanism, while allows significant reduction in configuration time. It also includes NDK integration for building JNI applications. This user guides provides details on how to use it and highlights the difference between the new plugin and the original plugin.

WARNING: Note that this is plugin is at the experimental stage. The Gradle API for the new component model is not final, which means it’ll only work with a specific version of Gradle until the APIs are final.

Additionally, the DSL is likely change significantly, as APIs to create the DSL are finalized.

This is a very early preview of the plugin for feedback on performance and NDK integration.

Requirements

Gradle (see section below for version required)

Android NDK r10e (if you are using NDK)

SDK with Build Tools at least version 19.0.0 and we aim to minimize the amount of changes needed for the migration process in the future. Some features may require a more recent version.

Gradle Requirements

Each version of the experimental plugin requires a specific version of Gradle. Here is a list of required Gradle version.

Plugin Version

Gradle Version

0.1.0

2.5

0.2.0

2.5

0.3.0-alpha3

2.6

0.4.0

2.8

0.6.0-alpha1

2.8

0.6.0-alpha5

2.10

Migrating from Traditional Android Gradle Plugin

A typical Android Studio project may have a directory structure as follows. File that needs to be change is highlighted in red:There are some significant changes in the DSL between the new plugin and the traditional one.

.

├── app/

│ ├── app.iml

│ ├── build.gradle

│ └── src/

├── build.gradle

├── gradle/

│ └── wrapper/

│ ├── gradle-wrapper.jar

│ └── gradle-wrapper.properties

├── gradle.properties

├── gradlew*

├── gradlew.bat

├── local.properties

├── MyApplication.iml

└── settings.gradle

./gradle/wrapper/gradle-wrapper.properties

Each version of the new plugin supports a specific Gradle version. The latest plugin (0.4.0) supports only gradle-2.8.

There are significant changes to the DSL of the plugin. We understand that many of the changes are frustrating and seem unnecessary, and our goal is to remove some of these current changes to minimize the migration process from the traditional plugin in the future.

DSL Changes:

Plugin name is com.android.model.application instead of com.android.application. Or use apply plugin: "com.android.model.library" if you want to create an Android aar library.

Configuration is wrapped with the model { } block

Most properties require the = operator

Adding elements to a Collection should be done using the add method.

Current DSL Limitations that will hopefully go away:

buildTypes, productFlavors and signingConfigs must be place outside of the android { } block.

Nested options within the android { } block must be configured using the with keyword.

Properties are only set with their direct types only, with no way to accept other types and adapting them. For instance:

Properties of type File accepts only File instead of File and String objects.

Signing Config

You can refer to another model element using the $() syntax. To use this syntax, "-Dorg.gradle.model.dsl=true" has to be added as an argument to the Gradle command line for version below 2.10. This is useful for specifying signing configs.

apply plugin: "com.android.model.application"

model {

android {

compileSdkVersion =23

buildToolsVersion ="23.0.2"

}

android.buildTypes {

release {

signingConfig = $("android.signingConfigs.myConfig")

}

}

android.signingConfigs {

create("myConfig") {

storeFile = new File("/path/to/debug.keystore")

storePassword = "android"

keyAlias = "androiddebugkey"

keyPassword ="android"

storeType ="jks"

}

}

}

Ndk Integration

The experimental plugin comes with NDK integration for creating native applications. To use the NDK integration:

Use the SDK Manager inside Studio to download the NDK.

Set ndk.dir in local.properties or the ANDROID_NDK_HOME environment variable to the directory containing the NDK.

Add an android.ndk block to the model in build.gradle.

The build.gradle of a simple NDK application may look like this:

apply plugin: 'com.android.model.application'

model { android { compileSdkVersion = 22 buildToolsVersion = "22.0.1"

}

android.ndk {

moduleName = "native"

}

}

*Note that the moduleName is required. It determines the name of the resulting native library.

Source Set

By default, it will look in src/main/jni for C/C++ file. Configure android.sources to change the source directory.

model { android { compileSdkVersion = 22 buildToolsVersion = "22.0.1"

}

android.ndk {

moduleName = "native"

}

android.sources {

main {

jni {

source {

srcDir "src"

}

}

}

}

}

The JNI source set may contain both C and C++ files. All files in the sub-directories are included. Files with extension '.c' is considered as C files, whereas C++ files has may have any of the following extensions: '.C', '.CPP', 'c++', '.cc, '.cp', '.cpp', '.cxx'. Files may be excluded with the exclude method, whereas include is ignored:

model {

android.sources {

main {

jni {

source {

include "someFile.txt" // This is ignored.

exclude "**/excludeThisFile.c"

}

}

}

}

}

Other Build Options

Various build options can be set within the android.ndk { } block. For example,

model { android { compileSdkVersion = 22 buildToolsVersion = "22.0.1"

}

android.ndk {

// All configurations that can be changed in android.ndk.

moduleName = "native"

toolchain = "clang"

toolchainVersion = "3.5"

// Note that CFlags has a capital C, which is inconsistent with

// the naming convention of other properties. This is a

// technical limitation that will be resolved

CFlags.add("-DCUSTOM_DEFINE")

cppFlags.add("-DCUSTOM_DEFINE")

ldFlags.add("-L/custom/lib/path")

ldLibs.add("log")

stl = "stlport_static"

}

android.buildTypes {

release {

ndk.with {

debuggable = true

}

}

}

android.productFlavors {

create("arm") {

ndk.with {

// You can customize the NDK configurations for each

// productFlavors and buildTypes.

abiFilters.add("armeabi-v7a")

}

}

create("fat") {

// If ndk.abiFilters is not configured, the application

// compile and package all suppported ABI.

}

}

// You can modify the NDK configuration for each variant.

components.android {

binaries.afterEach { binary ->

binary.mergedNdkConfig.cppFlags.add(

"-DVARIANT=\"" + binary.name + "\"")

}

}

}

Known Limitations

No support for using a NDK modules like cpu_features

No support for integrating external build systems.

Samples

Multiple NDK Projects

Plugin 0.4.0 added the preliminary support for NDK dependencies and the ability to create just a native library. Please be aware this is a preview of the direction we are going and the implementation is not complete. Note that while it is possible to compile the native project for Gradle, editing and debugging support in Android Studio is not yet implemented.

Standalone NDK Plugin

In gradle-experimental:0.4.0, a new plugin is created to allow creation of just the native library without creating an Android application or library. The DSL is similar to the application/library plugin. The following example build.gradle can create a libhello.so from sources in "src/main/jni"

apply plugin: "com.android.model.native"

model {

android {

compileSdkVersion = 21

}

android.ndk {

moduleName = "hello"

}

}

Known Issues

Editing support for the standalone plugin is not yet implemented in Android Studio

Modifying a source file in the library does not automatically cause the application to re-link the new library when building an application.

NDK Dependencies

The syntax for specifying dependency follows the style of Gradle's future dependency system. You can set a dependency on an Android project or a specific file.

For example, let say you have a subproject in "lib" using the standalone NDK plugin:

lib/build.gradle:

apply plugin: "com.android.model.native"

model {

android {

compileSdkVersion = 21

}

android.ndk {

moduleName = "hello"

}

android.sources {

main {

jni {

exportedHeaders {

srcDir "src/main/headers"

}

}

}

}

}

Any projects with a JNI dependency will include the directories specified in the exportedHeaders.. You can add dependency on the lib project from your application for your JNI code:

You can specify a build type and/or product flavor of your target project. Otherwise, the plugin will try to find the same build types and product flavor as your application. You can also specify the linkage type if you would like the native library to be linked statically. E.g.

Caveat: The next version will have a DSL change to follow Gradle's built in support for prebuilt library, similar to https://github.com/gradle/gradle/blob/master/subprojects/docs/src/samples/native-binaries/prebuilt/build.gradle.

You can add native dependency to either 'jniLibs' or 'jni' source set. When dependency is added to "jniLibs" the native library will be package into the application/library, but it will not be used for compiling the JNI code. E.g.